Loud-speaker



Oct. 8, 1929. M. c. HOPKINS LOUD SPEAKER 4 Sheets-Sheet Original FiledDec. 22, 1925 illlljlllllllllll lull' I.. lll liu l. Il llll l ll NewOct. s, 1929. M HOPKNS f 1,730,508

LOUD SPEAKER Original Filed Dec. 22, 1925 4 Sheets- Sheet 2iiiiiiii-iiiiiiiiiiiiiiiiiiill d Oct- 3, 1929- M. c. HOPKINS 1,730,508

LOUD SPEAKER Original Filed Deo. 22, 21,925v 4 Sheets-Sheet 5 GtbmmgaOct. 8, 1929. M C, HOPKlNs 1,730,508

I LOUD SPEAKER Y Original Filed Dec. 22, 1925 4 Sheets-Sheet 4 {Yy/ Umm@76 M /4 vvueno ara/3 Halo/m56 44 wmp@ )ffm M Patented Oct. 8, 1929UNITED STATES PATENT oFFIcE MARCUS C. HOPKINS, OF WASHINGTON, DISTRICT0F COLUMBIA, ,ASSIGNOR TO 'HOP- .'KINS CORPORATION, OF JERSEY CITY, NEWJERSEY, A CORPORATION OF DELA- WARE LOUD-SPEAKER Application filedDecember 22, 1925, Serial No. 77,030. Renewed April 15, 1929.

The present invention embraces a loud speaker suitable for use on aradio receiving set, and also suitable for use'as an annunciator onwired radio systems, and in general, wherever speech current is to betranslated into/audible sound.

It is an object of the present invention to produce a translating deviceof the cone type whereby clarity of tone and faithfulness in translatingmay be attained with reliability and at low cost. The preferred form ofthe device embodies an electrical movement of rugged constructionwherein the vibrating armature is made up of a plurality of resilientplates spaced apartA from one another to give good flexibility, theseplates being of ample width and thickness so that in the aggregate theyform a path of low magnetic reluctance. The cone to which this vibratoryarmature is connected may bel of paper, or

like material, and preferably has lits outer tion edge bent forward toform a brim or rim by which the cone is yieldingly attached to anannular wood frame 'capable of acting as a resonator to supplement thesound producing action of the cone. v

Other objects and advantages will become clear from the followingdetailed description taken in conjunction with the accompanying drawingswhereinl Fig. l is a front speaker;

Fig. 2 is a side elevation of the same;

Fig. 3 is a sectional elevation on the line 3-3 of Fig. 4

Fig. 4 is a front elevation with the paper cone removed to disclose theelectrical movenient; .l

Fig. 5 vshows the electrical movement in front elevation'with certainparts in section;

Fig.- 6 -shows said element in side elevaelevation of the loud Fig. 7 isa transverse section on the line 7-7 of Figu;

Fig. 8 is a plan view of the electrical movement; j

Fig. 9 is a sectional detail of the laminated armature thereof; 'y

Fig. 10 shows the slots in the adjustable pole shoe of the unit, andFig. ll is a detail of one of the pole pieces.

'The preferred embodiments disclosed in the drawings comprise a woodbase l having a slot in which is glued the lower edge of a circularresonator 2. AThis resonator is preferably made of three ply wood. Threeply fir three eighths of an inch thick is suitable, and there isadvantage in having the grain of the inner ply 3 disposed at rightangles to the grain of the two adjacent outer plies. An annular groove 4is turned in this resonator, and at the outer edge of this groove `thewood is beveled at 5 to form a seat to which may be glued the outwardlybent brim 6 of the sound producing cone 7. This cone may be made ofpaper. Paper of the quality known as'cover paper is suitable. The conecan be cut from a flat sheet and then bent into shape and glued along aradial seam. The outer edge of the conical. structure so formed is thenbent at 8 to form an outwardly flaring brim. The brim will naturallytake on a frusto conical form making an angle to the vertical planesubstantially equal to the angle at which radial elements of the coneintersect the vertical plane. It is important thatl the outer part onlyof this brim 6 be fastened to the woodresonator at the beveled surface 5for the inner portion of the brim is relied on to form a resilientsupport or hinge whereby the cone 7 may move` bodily without substantialdistortion. For a paper cone 12 in outside diameter the brim may be 1%of an inch wide and the glued portion may have a width of lih orthereabout.

The electrical movement'for actuating the cone comprises a permanentmagnet 9 suitably clamped to the wooden disc 2 as by a cross bar 10 andmachine screw l11. Secured to pole 12 of the ma net by a screw 13 (Fig.5) is a pole piece 14 o irregular shape. This pole provided with a polepiece 18V`l1eld in place 100..

by a screw 19 and carrying a transverse bolt 20 whereby the vibratoryarmature is supported.

The vibratory arma-ture consists of a plurality of blued steellaminations 21, say four in number, spaced apart on bolt 20 by ironwashers 22, with"which the laminations make close magnetic contact. `Attheir other ends the laminations are spaced apart by soft iron washers23, and are held in close contact therewith by a soft iron element 24,one end of which is riveted over to form an annu.- lar ange 25 tightlyholding the laminations and Washers' together. This element 24 is inpart hollow to receive a transmission rod 26, preferably made ofphosphorbronze and se cured to element 24 by solder 27. The forward endof the transmission rod 26 passes through a hollow rivet 28 at the apexof the cone, and may there be rigidlyl attached by a soldered connection29 (Fig. Or if desired, as shown in Fig'. 6, a set screw 30 may be usedin place of or as supplemental to a soldered connection 31. Conicalbrass plates 32 and 33 serve to strengthen the apex of the cone and areheld in ti ht engagementwith the paper at the apex o? the cone by thehol low rivet 28.

The electromagnet to which 'speech current is delivered for actuating'the armature comprises a simple solenoid 34. About 6000'turns of No.40'enameled wire mounted on a bakelite or composition spool 35 issuitable for this pur ose. An insulating face late 36 may be, use as aguide and anchor or the leading in wires 37 and 38. Mounted to movewithin this coil is a soft iron pole shoe 39, a portion of which isthreaded at 40 for engagement with threads cut inthe pole piece 14.There is also provided a knob 41 positioned at the back of the Woodresonator and by which pole shoe v39 may be advanced or retracted toincrease or decrease the air gap between it andy the opposing element24. The pole shoe is preferably provided with intersecting slots42 and43 (Fig. 10) to reduce eddy currents.

Fig. 1 shows pole piece 14 in rear elevation.

`I find that it is advantageous to first drill this pole piece toreceive the threaded pole shoe 39 and then to slot it at 44 through thetapped hole. The two fingers` thus produced are then squeezed inwardtoward one another by such an extent as may be needed to giveI africtional grip on the threadedportion 40 of the pole shoe 39. Thisprevents that` pole shoe from working loose duringl shipment and alsoholds the pole shoe in ri id position irrespective of the vibrationto'which the ole shoe is subjected when in actual use. is slot 44 hasthe further function of 4reducing eddy current losses in that-part ofthepole piece lying nearest to coil 34. This one ex- .pedient increases theeffectiveness of the device to a very noticeable extent. with theelements constructed and arranged as above described a speech currentpassed through winding 34, as from a radio receiving set or a wireannunciator system or circuit, will produce a corresponding vibration,of the laminated armature and such movement of the transmission rodv 26as to translate the electrical impulses into audible sound thereby ineii'ect reproducing the speech or other signal represented by the speechcurrent.

The conical diaphragm 7 can mo've bodily because of its lyieldingorhinged connection with the Wood resonator, and I have found is capableof transmitting its vibrations through the hinge to the wood. This isparticularly true with respect to tones low in the musical scale. TheWood taires up the vibrations and together with the cone transmits thevibra.- tions to the surrounding air with results that are highlysatisfactory.' The pole shoe can be advanced or retracted through coil34 by suitably manipulating the knob 41, and in this mannerthe Width ofthe air gapV can be coordinated to the strength of the signals beingreceived'. Any .expansion or contraction of the diaphragm due toatmospheric conditions is not of serious consequence because the freeend of the armature can move with the cone and readjustment of the airgap to rcompensate for such changes requires nothing more thanvmanipulation of knob4l.

I attach very considerable importance to the use of a laminatedvibratory element or armature. The laminations can be wide enough sothat in the aggregate they afford a largecross section and a resultinglow magnetic reluctance, while at the same time have ygood resilience.The armatures` resist-ance to bending does not increase as rapidly aswould be the case ifthe armature were of solid metal of thesameaggregate cross section. i In addition, the movements of thetransmission rod 26 are more nearly axial than if this rod were rigidlyattac-hed near the end of a solidvibratory armature. Within the narrowrange of movement incident to normal use the successive positions of rod26 are almost in parallel relation to one another.

The loud speaker or annunciator above described may bemade in varioussizes, and is compact, rugged, and .inexpensive to build. When builtyinto a radio receiving set or cabinet, 'or when used as an accessory inother resonator but leaving a part of the brim free n i to act as ahinge.

Also in my copending application, Serial No. 7 7 ,029, filed December22nd, 1925, claims are presented on the use of a Wood panel the outerportion of which serves as a resonator,

and the inner portion of which serves as the support for theelectrically actuating unit.

I claim: l

1. In a loud speaker,.the combination of a speech coil and a vibratoryarmature therefor, said armature comprising a plurality of spacedlaminations, andmagnetic inserts arranged at intervals transversely ofsaid laminations to retain them in spaced relation.

2. In a loud speaker the combination of a speech coil, a polarizedvibratory armature therefor, said armature comprising a plurality oflaminations spaced apart at their ends by iron inserts.

3. In a cone type loud speaker, the combination vof a magnet, a polepiece secured to each pole of said magnet, one of said pole pieceshaving a flat surface lying in a plane substantially parallel with theplane of the 1nagnet, a speech vcoilf housed within said magnet with itsaxis at right angles to the plane of the magnet and mounted against saidflat surface of one of the pole pieces, a pole shoe movable forward orbackward through said coil, a polarized armature secured at one end tothe opposing pole piece, and a transmission rod secured to saidarmature.

4. In a cone type loud speaker, the combination of a permanent magnet, apole piece secured to each pole of said magnet, a speech coil mounted onone'of said pole pieces, a pole shoe passing through saidA coil andhaving threaded engagement with its pole piece, said threaded engagementpermitting advancement or retraction of said pole piece, a polarizedarmature rigidly secured to the opposing pole piece, and a transmissionrod securedl to said armature and adapted to move with a substantiallyaxial movement to transmit energy to sound producing means.

5. In a cone type loudspeaker the combination of a permanent magnet, apole piece secured to each pole of said magnet, one of said pole pieceshaving a ilat surface lying in a plane substantially parallel with theplane ofthe magnet, a speechcoil housedy within said magnet with itsaxis atA right angles to the plane of the `magnet and mounted againstsaid ilat face of'one of the pole pieces, a pole shoe passing throughsaid coil and having threaded engagement lpermitting its advancement orretraction through said coil, a polar'- ized armature secureil to theopposing pole piece and carrying a magnetizable element opposite saidadjustable pole shoe, and a transmission rod secured to saidmagnetizable element for transmitting energy to sound producing means.

6. In a cone type bination of a magnet, a pole piece secured to eachpole of said magnet, a speech coil housed within said magnetsubstantially coaxial therewith and mounted against the flat surface ofoney of said pole pieces, a pole shoe movableforward or backward throughsaid coil, a polarized armature secured at one end to the opposing polepiece said armature comprising laminations spaced apart fora partatleast of their length, a magnetizable element securing the oppositeends of said laminations, and a transmission rod secured to saidmagnetizable element.

7 In a cone type loud speaker the combination of a permanent magnet, apole pie secured to each pole of said magnet, a speech coil mounted onone of said pole pieces, a pole shoe assing through said coil and havingthrea ed engagement with its pole piece, said. threaded engagementpermitting advancement or retractlon of said pole piece, a polarizedarmature rigidly secured to the opposing pole piece, and comprising aplurality of laminations spaced apart for a part of their length, amagnetizable element clamping the opposite ends of said laminations, anda transmission rod rigidly secured to said magnetizable element andadapted to move with a substantially axial movement totransmit energy tosound producing means.

8. In a cone type loud speaker the combination of a permanent magnet, apole piece secured to each pole of said magnet, a speechcoil housedwithin said magnet and mounted against one of said pole p1eces'a.pole-shoe passing through said coil and lhaving a threaded engagementpermitting advancement or retraction through Saidcoil, fasten- -ingmeans passed through the opposing pole piece, a laminated armature heldin position thereby, a magneti'zable element clamping the opposite endsof-.said laminations, and a transmission rod secured to saidmagnetizable element and actuated thereby to transmit energy to soundproducing means, substantially as described.

9. In a cone type loud speaker the combination of a permanent magnet, apole piece bolted to each pole of said magnet, a speech.

coil housed within said magnet and mounted against the iiat face of oneof said pole pieces, a slotted pole shoe passing through said coil andhaving threaded engagement with its pole piece and having meansv wherebythe pole shoe may be rotated for advancement or retraction through saidcoil, fastening means passed through the-opposing pole piece, ironlaminations and iron 4washers between their ends thereby to provide apolarized armature of large cross section. and relatively highresiliency, and a transmission rod secured to said polarized armatureand adapted to move with a substantially axial movement to transmitenergy to sound producing means.

loud speaker the coms l0. In a cone'type loud speaker the combination ofa permanent magnet, a stamped pole piece bolted to each pole of saidmagnet, each of said pole pieces having an extension with integral lugsengaging an end of the magnet to insure rigidity of the boltedconnection, a speech coil housed Within said magnet substantiallycoaxial therewith and mounted against the Hat face of one of said pole,pieces, a slotted pole shoe passing through said coil. andshavingthreaded en gagement with its pole piece and having a knlob whereby thepole shoe may be rotated for advancement or retraction through saidcoil, a bolt passed through the opposing pole piece, iron laminationsand iron washers threaded alternately on said bolt and held in closeengagement thereby, a magnetizable element clamping the opposite ends ofsaid laminations with iron Washers between said ends, thereby to providea polarized arma- .ture of large cross section and relatively highresiliency, and a transmission rod secured to said magnetizable elementand adapted to move with a substantially axial movement to transmitenergy to a sound producing cone, substantially as described.

11. In a loud speaker, the combination of a speech coil, a pole shoepassing through said coil and a slotted pole piece into which said poleshoe is threaded and by which it is yieldingly gripped.

In a loud speaker, the combination o'f a speech coil, a polarizedvibratory armature therefor, a pole piece on which one end of said coilis seated, and a pole shoe passing through said coil into operativerelation Wit-l1 said armature, said pole shoe having threaded engagementWith said pole piece, and said po e piece being slotted in that portionad- ]acent to the coil thereby to. reduce eddy current losses.

13. In a loud speaker, the combination ofa speech coil, an armaturetherefor, a pole piece on which said coil is mounted, said pole piecebeing'slott'ed adjacent to said coil to reduce eddy current losses and apole' shoe passing through said pole piece and movable toward and fromthe free end of said armature to regulate the width of its air gap.

14. In a loud speaker, the combination of a speech coil, a polarizedarmature therefor, a pole piece against the flat face of which said coilis mounted, said pole piece having a threaded opening thereinand'a slotintersect-ing said opening to forma pair of fingers, and va pole shoethreaded through said opening and yieldingly gripped therein by saidfingers, saidv pole shoebeing movable toward or from the free-wend ofsaid armature to.

regulate the width of its air gap.

15. In a loud speaker, the combination of a speech coil and a vibratoryarmature therefor, said armature comprising a plurality of laminationsofmagnetizable material whereby relatively loW reluctance and highresilience is obtained.

16. In a loud speaker, a permanent magnet, aspeech coil housed withinsaid magnet with its axis substantially at right angles to the plane ofthe magnet, a pole piece connected to one pole of said magnet andconnected to one end of said speech coil, and a vibratory armatureconnected to the other pole of said magnet andarranged adjacent theother end of said speech coil.

17. In a loud speaker, a permanent magnet, a speech coil housed Withinsaid magnet With its axis substantially at right angles `to the plane ofthe magnet, a pole piece connected to one pole of said magnet andconnected to one end of said speech coil, a pole piece connected to theother pole of said magnet, and a vibratory armature carried by saidsecond pole piece and arranged adjacent the other end of said speechcoil.

In testimony whereof I afl'ix my signature.

MARCUS C. HOPKINS.

